A method for preparing a high-response full-diamond transparent electrode ultraviolet detector

Abstract

The application discloses a preparation method of a high-response full-diamond transparent electrode ultraviolet detector, which comprises the following steps: growing an intrinsic diamond epitaxial layer and a heavy boron-doped diamond layer on an intrinsic single crystal diamond substrate, and performing oxygen treatment on the surface; forming an interdigital photoresist mask on the heavy boron-doped diamond layer after the oxygen treatment, etching the area without the mask into the epitaxial layer; removing the mask, and performing oxygen atmosphere annealing treatment on the sample to obtain the detector. The etching defects are passivated and removed by using the oxygen atmosphere annealing, the problems of complex secondary epitaxial process, high cost and slow response speed caused by boron atom diffusion of the current full-diamond transparent electrode ultraviolet detector are solved, the response of the diamond ultraviolet detector is improved, the high response speed is maintained, and the method has a good application prospect.

Description

Technical Field

[0001] This invention belongs to the field of photoelectric detection technology, specifically relating to a method for preparing a high-response, all-diamond transparent electrode ultraviolet detector. Background Technology

[0002] Ultraviolet (UV) photoelectric detection technology has important applications in key fields such as space flame monitoring, smoke alarms, and space communication. Because these applications typically operate in extremely harsh environments, they place very high demands on the performance of detector materials. Compared to conventional semiconductor materials (such as silicon), diamond possesses superior properties such as a wide bandgap (5.47 eV), high thermal conductivity (2200 W / mK), strong radiation resistance, and high resistivity, making it considered an ideal material for fabricating UV detectors. Traditional diamond UV detectors typically use metals (such as Au, Ti, and W) as electrode materials. While metal electrodes offer good conductivity and high stability, their opacity blocks some incident UV light, reducing the effective light absorption area and limiting the improvement of detector responsivity. Furthermore, deep-level defects at the metal-diamond interface affect carrier transport, thus reducing the device's response speed. While using transparent electrodes such as graphene and ITO can increase the light absorption area, they still face the problem of limited response speed due to interface lattice mismatch, and high interface state density also leads to a decrease in responsivity.

[0003] Therefore, using boron-doped diamond as the electrode material to construct an all-diamond ultraviolet detector has become an effective solution. Boron-doped diamond possesses excellent optical transparency and forms a homojunction with the diamond substrate, eliminating lattice mismatch issues and resulting in high interface quality, which is beneficial for simultaneously improving the device's responsivity and response speed. However, when fabricating transparent electrode devices, an etching process is typically required to define the electrode region. This process introduces etching defects on the surface of the active region, which can trap photogenerated carriers and affect device performance. To suppress etching defects, existing technologies employ secondary epitaxial growth of diamond thin layers for defect repair. However, this method requires the use of MPCVD equipment again, leading to process complexity and increased costs. Furthermore, during the secondary epitaxy process, boron atoms within the boron-doped electrode may diffuse into the newly grown layer, adversely affecting the device's response speed.

[0004] Therefore, there is an urgent need to develop a low-cost defect suppression method to effectively overcome the aforementioned process defects and boron diffusion problems while ensuring high responsivity and high response speed of the device, thereby promoting the further development of all-diamond ultraviolet detectors towards high performance and low cost. Summary of the Invention

[0005] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0006] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0007] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a method for fabricating a high-response all-diamond transparent electrode ultraviolet detector.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for fabricating a high-response all-diamond transparent electrode ultraviolet detector, comprising the following steps: An intrinsic diamond epitaxial layer and a boron-doped diamond layer were sequentially grown on an intrinsic single-crystal diamond substrate using MPCVD technology, and the surface of the boron-doped diamond layer was subjected to oxygen treatment. Photoresist is coated onto a boron-doped diamond layer, and after exposure and development, the photoresist forms an interdigitated mask. The boron-doped diamond region not protected by photoresist was etched by ICP until the intrinsic diamond epitaxial layer was exposed. After removing the photoresist, a diamond detector with boron-doped diamond interdigitated electrode structure was obtained. The detector was annealed in an oxygen atmosphere to obtain a fully diamond transparent electrode ultraviolet detector.

[0009] As a preferred embodiment of the preparation method described in this invention, the intrinsic single-crystal diamond substrate is a type of high-temperature high-pressure synthetic diamond or CVD synthetic diamond, with a crystal orientation of (100), a surface roughness of less than 10 nm, a nitrogen impurity concentration of less than 1 ppm, and a boron impurity concentration of less than 10 ppb.

[0010] As a preferred embodiment of the preparation method described in this invention, the intrinsic diamond epitaxial layer is grown under a pressure of 90-120 Torr, a methane flow rate of 5-20 sccm, a hydrogen flow rate of 400-500 sccm, a temperature of 1000-1100℃, and a growth thickness of 100-1000 nm.

[0011] In a preferred embodiment of the preparation method described in this invention, the growth pressure of the boron-doped diamond layer is 100-130 Torr, the hydrogen flow rate is 400-500 sccm, the methane flow rate is 2-10 sccm, the B / C ratio is ≥600ppm, the growth temperature is 850-1100 ℃, the growth thickness is 10-50 nm, and the doping concentration is ≥10.18 cm -3 .

[0012] As a preferred embodiment of the preparation method described in this invention, the oxygen treatment method is one of ultraviolet ozone treatment, high-temperature heating of a sulfuric acid / nitric acid mixed solution, or oxygen plasma treatment.

[0013] In a preferred embodiment of the preparation method described in this invention, the photoresist thickness is greater than twice the thickness of the boron-doped diamond layer, the interdigitated width of the interdigitated photoresist mask is 1-20 μm, and the interdigitation distance is 1-10 μm.

[0014] In a preferred embodiment of the preparation method described in this invention, the ICP etching atmosphere is one or more of O2, Ar, Cl, F, and CF4.

[0015] As a preferred embodiment of the preparation method described in this invention, the ICP bias etching power is less than 30W, the etching thickness is greater than the thickness of the boron-doped diamond layer, and the etching depth in the intrinsic diamond epitaxial layer is 10-20nm.

[0016] In a preferred embodiment of the preparation method described in this invention, the annealing atmosphere is one of O2, air, O2 / Ar, or O2 / N2.

[0017] In a preferred embodiment of the preparation method described in this invention, the annealing temperature is 300-600℃, the annealing time is 5-20 min, and the higher the oxygen content, the shorter the annealing time.

[0018] Another objective of this invention is to overcome the shortcomings of the prior art and provide a high-response all-diamond transparent electrode ultraviolet detector. The high-response all-diamond transparent electrode ultraviolet detector has a stacked structure from bottom to top, comprising: an intrinsic single-crystal diamond substrate 1; an intrinsic diamond epitaxial layer 2; and a p-type heavy boron doped diamond electrode array 3.

[0019] Beneficial effects of this invention: This invention utilizes an oxygen atmosphere to anneal the sample. Oxygen preferentially reacts with etched defect sites, thereby passivating or removing defects and improving the device's responsiveness. The oxygen atmosphere annealing process is simple, low-cost, and conducive to industrialization. Oxygen atmosphere annealing does not cause the diffusion of boron ions, maintaining a high crystal quality in the intrinsic epitaxial layer, thus resulting in a fast device response speed. Attached Figure Description

[0020] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a three-dimensional schematic diagram of the high-response all-diamond transparent electrode ultraviolet detector of the present invention, wherein 1 is an intrinsic single-crystal diamond substrate; 2 is an intrinsic diamond epitaxial layer; and 3 is a p-type heavy boron doped diamond electrode array.

[0021] Figure 2 This is a cross-sectional view of the high-response all-diamond transparent electrode ultraviolet detector of the present invention, wherein 1 is an intrinsic single-crystal diamond substrate; 2 is an intrinsic diamond epitaxial layer; and 3 is a p-type heavily doped diamond strip electrode array.

[0022] Figure 3 This invention provides a comparison of the photocurrent of a high-response all-diamond transparent electrode ultraviolet detector, an all-diamond transparent electrode ultraviolet detector without oxygen atmosphere annealing, and a metal electrode diamond ultraviolet detector.

[0023] Figure 4 This invention provides a comparison of the transient response of a high-response all-diamond transparent electrode ultraviolet detector and an all-diamond transparent electrode ultraviolet detector that has not undergone oxygen atmosphere annealing in this embodiment of the invention. Detailed Implementation

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0026] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0027] Unless otherwise specified, all raw materials used in the embodiments of this invention are commercially available.

[0028] Example 1 like Figure 1The diagram shows a three-dimensional schematic of the high-response all-diamond transparent ultraviolet detector of the present invention. The structure stacked from bottom to top includes: an intrinsic single-crystal diamond substrate (1); an intrinsic diamond epitaxial layer (2); and a p-type heavy boron doped diamond electrode array (3).

[0029] The fabrication method of the above-mentioned high-response all-diamond transparent electrode ultraviolet detector is as follows: This embodiment provides a method for fabricating a high-response, all-diamond transparent electrode ultraviolet detector: (1) The substrate was a high-quality intrinsic single-crystal diamond substrate of type IIa with a crystal orientation of (100) synthesized by CVD, with a thickness of 300 μm. It was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min in sequence, and then purged with nitrogen for 20 s. Then it was placed in an MPCVD equipment to grow a 100 nm intrinsic diamond epitaxial layer and a 10 nm boron-doped diamond layer in sequence. The growth pressure of the intrinsic diamond epitaxial layer was 90 Torr, the methane flow rate was 5 sccm, the hydrogen flow rate was 500 sccm and the temperature was 1000 ℃. The growth pressure of the boron-doped diamond layer was 100 Torr, the methane flow rate was 2 sccm, the B / C ratio was 1200 sccm, the hydrogen flow rate was 480 sccm and the temperature was 1000 ℃. The doping concentration was 1×10 19 cm -3 Then, ultraviolet ozone treatment is used to convert the hydrogen terminals on the surface of the boron-doped diamond layer into oxygen terminals.

[0030] (2) A forked photoresist mask is formed on the surface of a boron-doped diamond layer using standard photolithography. The forked mask is 1 μm wide and the spacing is 1 μm. The unmasked area is etched for 20 nm in an ICP etching device with a bias power of 20 W. Then the photoresist mask is removed.

[0031] (3) The sample was placed in a rapid annealing device for annealing in a pure oxygen atmosphere at a temperature of 300°C for 20 minutes to obtain a high-response all-diamond transparent electrode ultraviolet detector.

[0032] Figure 2 This is a side cross-sectional view of the high-response all-diamond transparent ultraviolet detector of the present invention, wherein 1 is an intrinsic single-crystal diamond substrate; 2 is an intrinsic diamond epitaxial layer; and 3 is a p-type heavily doped diamond strip electrode.

[0033] Example 2 This embodiment provides a method for fabricating a high-response, all-diamond transparent electrode ultraviolet detector: (1) The substrate was a high-quality intrinsic single-crystal diamond substrate of type IIa with a crystal orientation of (100) synthesized under high temperature and high pressure, with a thickness of 500 μm. It was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min in sequence, and then purged with nitrogen for 20 s. Then it was placed in an MPCVD equipment to grow a 500 nm intrinsic diamond epitaxial layer and a 30 nm boron-doped diamond layer in sequence. The growth pressure of the intrinsic diamond epitaxial layer was 100 Torr, the methane flow rate was 10 sccm, the hydrogen flow rate was 490 sccm and the temperature was 1050 ℃. The growth pressure of the boron-doped diamond layer was 110 Torr, the methane flow rate was 5 sccm, the B / C ratio was 600 sccm, the hydrogen flow rate was 480 sccm and the temperature was 950 ℃. The doping concentration was 5×10 18 cm -3 Then, the hydrogen terminals on the surface of the boron-doped diamond layer are converted into oxygen terminals by high-temperature treatment with a sulfuric acid / nitric acid mixed solution.

[0034] (2) A forked photoresist mask is formed on the surface of a boron-doped diamond layer using standard photolithography. The forked mask is 10 μm wide and 5 μm apart. The unmasked area is etched for 45 nm in an ICP etching device with a bias power of 25 W. Then the photoresist mask is removed.

[0035] (3) The sample was placed in a rapid annealing device for annealing in a pure oxygen atmosphere at a temperature of 500°C for 10 minutes to obtain a high-response all-diamond transparent electrode ultraviolet detector.

[0036] Example 3 This embodiment provides a method for fabricating a high-response, all-diamond transparent electrode ultraviolet detector: (1) The substrate was a high-quality intrinsic single-crystal diamond substrate of type IIa with a crystal orientation of (100) synthesized by CVD, with a thickness of 1000 μm. It was ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min in sequence, and then purged with nitrogen for 20 s. Then it was placed in an MPCVD equipment to grow a 1000 nm intrinsic diamond epitaxial layer and a 50 nm boron-doped diamond layer in sequence. The growth pressure of the intrinsic diamond epitaxial layer was 90 Torr, the methane flow rate was 20 sccm, the hydrogen flow rate was 480 sccm and the temperature was 1000 ℃. The growth pressure of the boron-doped diamond layer was 100 Torr, the methane flow rate was 2 sccm, the B / C ratio was 1500 sccm, the hydrogen flow rate was 480 sccm and the temperature was 1100 ℃. The doping concentration was 1×10 20 cm -3 Then, ultraviolet ozone treatment is used to convert the hydrogen terminals on the surface of the boron-doped diamond layer into oxygen terminals.

[0037] (2) A forked photoresist mask is formed on the surface of a boron-doped diamond layer using standard photolithography. The forked mask is 20 μm wide and 10 μm apart. The unmasked area is etched for 70 nm in an ICP etching device with a bias power of 30 W. Then the photoresist mask is removed.

[0038] (3) The sample was placed in a rapid annealing device for annealing in a pure oxygen atmosphere at a temperature of 600°C for 5 minutes to obtain a high-response all-diamond transparent electrode ultraviolet detector.

[0039] Comparative Example 1 The difference between this comparative example and Example 1 is that an intrinsic diamond epitaxial layer is grown on the surface of an intrinsic single-crystal diamond substrate, and then the surface is treated to be oxygen-terminated. The detector is obtained by fabricating interdigitated metal electrodes using micro-nano fabrication technology, without the growth and etching of a heavy boron-doped diamond layer.

[0040] This comparative example is a conventional interdigitated metal electrode diamond ultraviolet detector, and the size parameters of its electrode array are the same as those of the device in Example 1.

[0041] Comparative Example 2 The difference between this comparative example and Example 1 is that annealing is not performed after removing the photoresist in step 3. This comparative example is a fully diamond transparent electrode ultraviolet detector before annealing, and the size parameters of its electrode array are the same as those of the device in Example 1.

[0042] Testing process: The sample is placed on the sample stage of the Agilent B1505A test equipment, and a voltage is introduced to the sample surface using a probe. The current signal of the device under light pulse is collected at a fixed voltage.

[0043] Figure 1 This is a three-dimensional schematic diagram of the high-response all-diamond transparent ultraviolet detector of the present invention. In this invention, 1 is an intrinsic single-crystal diamond substrate; 2 is an intrinsic diamond epitaxial layer; and 3 is a boron-doped diamond electrode array.

[0044] Photocurrent and dark current test conditions: Place the sample on the probe stage and attach two probes to the positive and negative electrodes respectively. In a dark environment, use an Agilent B1505A source meter to test the current between the positive and negative electrodes. The voltage scan range is -15V to 15V with a step size of 0.2V to obtain the dark current. Then, introduce 222nm light and repeat the test to obtain the photocurrent.

[0045] Comparison of detector performance between Comparative Examples 1 and 2 and Example 1 Figure 3As shown, it can be seen that the high-response all-diamond transparent ultraviolet detector of Example 1 has a larger photocurrent compared to the traditional metal electrode and the all-diamond transparent ultraviolet detector without annealing.

[0046] Response speed test conditions: Place the sample on the probe stage, and use two probes to attach to the positive and negative electrodes respectively. Use an Agilent B1505A source meter to test the current change curve between the positive and negative electrodes over time. The voltage is fixed at 20V. Obtain the photopulse current by switching on 222nm light.

[0047] Figure 4 A comparison of the transient responses of the high-response all-diamond transparent ultraviolet detector fabricated in this invention with that of the unannealed all-diamond transparent ultraviolet detector shows that the annealed device has a rise time of 0.14 s and a fall time of 0.03 s, while the unannealed device has a rise time of 0.15 s and a fall time of 0.04 s. The results indicate that the high-response all-diamond transparent ultraviolet detector of this invention has higher sensitivity while maintaining its response speed characteristics.

[0048] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A method for fabricating a high-response, all-diamond transparent electrode ultraviolet detector, characterized in that... :include, An intrinsic diamond epitaxial layer and a boron-doped diamond layer were sequentially grown on an intrinsic single-crystal diamond substrate using MPCVD technology, and the surface of the boron-doped diamond layer was subjected to oxygen treatment. Photoresist is coated onto a boron-doped diamond layer, and after exposure and development, the photoresist forms an interdigitated mask. The boron-doped diamond region not protected by photoresist was etched by ICP until the intrinsic diamond epitaxial layer was exposed. After removing the photoresist, a diamond detector with boron-doped diamond interdigitated electrode structure was obtained. The detector was annealed in an oxygen atmosphere to obtain an all-diamond transparent electrode ultraviolet detector.

2. The preparation method according to claim 1, characterized in that: The intrinsic single-crystal diamond substrate is a type of high-temperature high-pressure synthetic diamond or CVD synthetic diamond, with a crystal orientation of (100), a surface roughness of less than 10 nm, a nitrogen impurity concentration of less than 1 ppm, and a boron impurity concentration of less than 10 ppb.

3. The preparation method according to claim 1, characterized in that: The intrinsic diamond epitaxial layer is grown under a pressure of 90-120 Torr, a methane flow rate of 5-20 sccm, a hydrogen flow rate of 400-500 sccm, a temperature of 1000-1100 ℃, and a growth thickness of 100-1000 nm.

4. The preparation method according to claim 1, characterized in that: The growth pressure for boron-doped diamond layers is 100-130 Torr, the hydrogen flow rate is 400-500 sccm, the methane flow rate is 2-10 sccm, the B / C ratio is ≥600 ppm, the growth temperature is 850-1100 ℃, the growth thickness is 10-50 nm, and the doping concentration is ≥10. 18 cm -3 .

5. The preparation method according to claim 1, characterized in that: Oxygen treatment methods include one of the following: ultraviolet ozone treatment, high-temperature heating of a sulfuric acid / nitric acid mixed solution, and oxygen plasma treatment.

6. The preparation method according to claim 1, characterized in that: The photoresist thickness is more than twice the thickness of the boron-doped diamond layer. The interdigitated photoresist mask has an interdigitated width of 1-20 μm and an interdigitated spacing of 1-10 μm.

7. The preparation method according to claim 1, characterized in that: The ICP etching atmosphere includes one or more of O2, Ar, Cl, F, and CF4; the ICP bias etching power is less than 30 W, the etching thickness is greater than the thickness of the boron-doped diamond layer, and the etching depth in the intrinsic diamond epitaxial layer is 10-20 nm.

8. The preparation method according to claim 1, characterized in that: Annealing atmospheres include O2, air, O2 / Ar, and O2 / N2.

9. The preparation method according to claim 1, characterized in that: The annealing temperature is 300-600℃, and the annealing time is 5-20 minutes.

10. The high-response all-diamond transparent electrode ultraviolet detector prepared by the preparation method according to claims 1-9, characterized in that: The high-response all-diamond transparent electrode ultraviolet detector has a stacked structure from bottom to top, including an intrinsic single-crystal diamond substrate (1); an intrinsic diamond epitaxial layer (2); and a p-type heavy boron doped diamond electrode array (3).

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